Apertured fluorescent lamp with lens along the aperture



y 22, 1969 R. A. MENELLY ETAL 3, 7,

APERTURED FLUORESCENT LAMP WITH LENS ALONG THE APERTURE Filed July 1, 1966 2 Sheets-Sheet 1 FGJE LAWRENCE ,W. KIMBALL RICHARD A. MENELLY I N VEN TORS TTORNEY July 22, 1969 R. A. MENELLY ETAL 3,457,447

APERTURED FLUORESCENT LAMP WI 'I'H LENS ALONG THE APER'I'URFJ Filed July 1, 1966 2 Sheets-Sheet 2 FIG. l4 4 5 4 3 2 I O I 2 3 4 5 DISTANCE BELOW DISTANCE ABOVE CENTER CENTER FIG.I3

LAWRENCE W. KIMBALL RICHARD A. MENELLY I N VEN TORS BMM ATTORNEY United States Patent 3,457,447 1 APERTURED FLUORESCENT LAMP WITH LENS ALONG THE APERTURE Richard A. Menelly, Danvers, and Lawrence W. Kimball,

Bedford, Mass., assignors to Sylvania Electric Products Inc., a corporation of Delaware Filed July 1, 1966, Ser. No. 569,755 Int. Cl. H01k 61/35 US. Cl. 313-110 Claims ABSTRACT OF THE DISCLOSURE A fluorescent lamp is described having an aperture in its fluorescent coating, with a lens in register with the aperture and close to, generally aflixed to, the lamp. The lens is shown inside and outside the lamp.

This invention relates to fluorescent lamps in which a considerable portiton of the light is emitted in a particular direction, such as so-called reflector fluorescent lamps and apertured fluorescent lamps. A large part of the light from such lamps is emitted through a longitudinal aperture in a reflector coating or in a phosphor coating.

The reflector fluorescent lamp is used to project more light, generally downward, upon a plane surface, with, in that case, less light spread. Such lamps may be used advantageously in so-called strip lighting to allow the illumination of the reflector surfaces usually provided in lighting fixtures.

The apertured lamp, in which the apparent brightness observed at the aperture may be 10 to 50 times normal brightness, depending upon design, is -very adaptable to, and is used frequently in, photocopy applications.

In such applications the intensity of the luminous flux emerging from the aperture, the uniformity of the light falling upon the material to be copied, and the time of exposure are of great importance in achieving image clarity and quality of print.

In order to improve these features in some photocopy machines, the copy is positioned very close to the aperture, sometimes even touching it, in order to achieve greater intensity and to overcome normal scattering or diffraction of the light rays. In other machines a number of lamps are employed, being positioned to intensify the light falling upon the copy surf-ace. In these machines, baflles and auxiliary devices may be required to keep both stray and directed light from direct imaging either on the copy or the photocopying lens.

We have discovered that some of these disadvantages can be overcome by the incorporation of a lens extending partially or for the whole length of the aperture in order to direct the luminous flux in a path of narrower width and greater intensity. The lens may be transparent plastic or glass of suitable optical quality and design and is either attached to the aperture by adhesive or a mechanical holder or may be an integral part of the lamp envelope and be formed either at tube drawing or subsequent molding process. The lens and lamp can be cemented together to form an integral unit.

Because the lamp with a lens concentrates and directs the luminous flux from the aperture to a better degree than a non-lens lamp, certain advantages are attained. Greater light intensity falling on the copy surface will allow greater printing speed or may permit the employment of fewer lamps to obtain a required light intensity.

Lamp placement in a machine may be further from the copy because of the greater light intensity and better control of the light path. This is a, very desirable and sought-after feature with most photocopy machines.

The baflles and auxiliary reflectors required in some 3,457,447. Patented July 22, 1969 ice present photocopy machines, increasing the cost and the complexity of design features, may be eliminated or substantially reduced if the desirable features of the lens lamp are employed.

Photometric tests on lamps with aflixed lenses show a 26% increase in forward apertured beam brightness on a Sylvania F18T8/ GR/ 30 aperture lamp compared to similar lamps without lenses. F18T12/GR/30 apertured lamps showed a 30% increase in forward light using affixed lenses. The use of a lens results in a light output pattern of narrower width and of greater intensity.

Photocopy tests using the lamp with affixed lenses in several types of photocopy machines show an increase in printing speed up to 25% and an improvement in image clarity and quality of print.

The lamps used in the trials and which are the subject of this invention were made by afiixing a half-inch /2") diameter polished transparent acrylic plastic rod the whole length of the aperture of a F18T8/H.O./GR/ 30 apertured lamp. The rod was fastened to the lamp with a clear adhesive cement.

Other objects, advantages and features of the invention Will be apparent from the following specification taken in connection with the accompanying drawing, in which:

FIGURE 1 shows a form of the invention in which an apertured lamp of circular cross-section has a convex lens outside its aperture.

FIGURE 2 shows the same lamp with a rod of circular cross-section, except where it is in contact with the lamp surface, used as a lens.

FIGURE 3 shows the same lamp with a lens of another shape.

FIGURE 4 shows an apertured lamp having a crosssection in which the bulb is flattened.

FIGURE 5 shows the bulb indented to receive a lens.

FIGURE 6 shows a bulb flattened at the lens position.

FIGURE 7 shows a lamp with an entirely integral lens, attached to the inside surface of the bulb.

FIGURE 8 shows the same bulb with an attached refiector.

FIGURE 9 shows a lamp with an external reflector and an internal lens.

FIGURE 10 shows a lamp with the lens formed as an integral part of the bulb.

FIGURE 11 shows a different shaped lens formed into the bulb.

FIGURE 12 shows a still different shaped lens formed in the bulb.

FIGURE 13 is a pair of graphs, one showing the light distribution over the aperture without a lens and the light distribution with the rod-shaped lens of FIG. 2.

FIGURE 14 shows a perspective view of the claim of FIG. 2.

In FIG. 1, the glass bulb 1, shown in cross-section, has the phosphor coating 2 on the major portion of its interior surface with the minor portion of the bulb uncoated to form a longitudinal aperture 3. Just outside the aperture is the convex lens 4, which can be supported from a convenient surface, outside the bulb, or held to the bulb itself by connecting thereto, holding it by straps passing around the bulb, by cement or in some other suitable manner.

FIGURE 2 is the same except that the convex lens is replaced by a transparent rod 5, preferably of glass or plastic, held in the same way as the convex lens 4 of FIG. 1, for example, by connecting it thereto.

In FIG. 14, the elongated tubular nature of the lamp of FIG. 2 is apparent. A base 6, having contact pins 7 and 8, is attached in the usual way to each end of the lamp tube 1. The lenses in the other figures will be lon gitudinal and in positions similar to that of rod 4.

. 'In ,FIG. 3, the lens 9 is of a truncated shape with its rearv surface in contact with the outer surface ofthe tube 1. The side 20 can be made flat and at an outwardly extending angle such that a considerable portion of the light at the sides strikes at the proper angle, for total reflection or can be silvered to reflect light. A considerable gain 'in'fo'rward light output can be obtained in this manner.

In FIG. 4, the tube 1 has the fiat portion 10 and in FIG. 5 the tube has the concave portion 11, into which the rear surface of the lens 4 fits closely, being cemented thereto by a, suitable adhesive. In FIG. 6 the glass tube 1 is flattened at the aperture 12.

FIGS. 7 and 9 show a convex lens 13 fitted against the inside surface 14 of the tube 1, with the reflector portions 15, 16 cemented or otherwise aflixed to the bulb. In FIG. 8, an external lens is held between the reflectors 15, 16. p In FIGS. ,10, 11 and 12, the lenses 17, 18, 19 are molded into the tube 1. The lens portion extends longitudinally along the bulb and can be formed very simply at the drawing of the tubing or in a molding process, or even formed by heating the bulb to the softening point and molding it just prior to its use in lamp manufacturing.

FIGURE 13 shows a curve A of the light distribution along the circumference of the aperture when a polished clear acrylic rod is used as the lens, and aligned with the aperture. The tube was about 1 in outside diameter, and the rod about /2" in diameter. The curve B for the control that is the lamp without the rod-lens, shows the light emitted in directions above and below the middle of the aperture, the middle being taken as zero. The curve B is fairly broad, not dropping to half-intensity until three inches from the middle. On the other hand, the light with the rod lens in place is much narrower, dropping to half intensity at about 1 inch off the middle of the aperture, and giving nearly 25% more light in the middle of the aperture.

The light intensity in each case was measured on a plane surface three inches distant from the lamp tube 1.

What we claim is:

1. A substantially tubular fluorescent lamp in which the major portion of the light is emitted from a minor portion of the circumferential surface, said portion extending longitudinally along the tube, said lamp including a sealed 4 tubular envelope, a fluorescent coating on the interior surface of said envelope and defining said major portion, said coating having a longitudinal aperture therein and defining said minor portion, and a lens extending longitudinally along'said minor portion and incontact therewith to concentrate the light from said portion. 7 2. The combination of claim 1, in which the lamp is of circular cross section for most of its circumference with aflattened portion over the remainder of its circumference. i I l 3. The combination of claim 1 in which the tubular lamp has a concave portion along the aperture'and a convex lens'is fitted into said concave portion.

4 The lamp of claim 1 in which the tubular lamp h-as a fiat portion across the aperture, and a lens is attached to the flat portion. I I

i 5. The lamp of claim 1 in which the tubular lamp has a lens inside it along the aperture.

6. The lamp of claim 1 in which the lamp has reflecting portions extending outwardly along the edge of the aperture.

7. The lamp of claim 1 in which the tubular lamp has a lens formed integrally in its outside surface.

8. The lamp of claim 1 in which the lens may have flat surfaces along its edge to reflect and direct light through the lens face.

9. The lamp of claim 11, in which the fiat surfaces are silvered to reflect light back through the lens.

10. The combination of claim 1, in which the lens is a cylindrical plastic ro'd affixed to said envelope.

References Cited UNITED STATES PATENTS ROBERT SEGAL, Primary Examiner V. LAFRANCHI, Assistant Examiner US. Cl. X.R. 313-109 

